1. Field of the Invention
The present invention relates to heat dissipation, more particularly, to a heat dissipating structure formed by extrusion molding having enhanced air cooling performance.
2. Related Art
Referring to FIGS. 1A and 1B, an air-cooling heat dissipating structure 1 in the prior art is shown. The air-cooling heat dissipating structure 1 essentially includes a substrate 2 and fins 3 formed on the substrate 2. The substrate 2 is provided for contacting a heat source, or serves as a casing to enclose a heat generating member. An inner surface of the substrate 2 absorbs heat of a heat source 4 or a heat generating member 5 through heat conduction or heat convection, and an outer surface of the substrate 2 exchanges heat with ambient air to dissipate heat through heat convection. The fins 3 are disposed on the outer surface of the substrate 2 and arranged in parallel. The fins 3 are provided for increasing the total surface area for heat exchange, to enhance the heat convection performance of the air-cooling heat dissipation structure.
In general, the heat dissipating structure in the prior art is fabricated by various methods, such as machining, die casting, extrusion molding, and combination process. The extrusion molding method is widely applied to fabricate members of a uniform cross-sectional shape, due to its high production rate and simple processes. The extrusion molding method using aluminum or aluminum alloy with a relatively low melting point is also referred to as an aluminum extrusion molding method.
As aforementioned, the air-cooling heat dissipating structure is applied to serve as a casing to enclose a heat generating member. The heat generated by the heat generating member is indirectly dissipated outside through the air-cooling heat dissipating structure. The heat generating member is also directly cooled by air flowing into the casing to achieve an enhanced heat dissipation performance. In order to allow the circulation of the air flows, air vents formed on the casing are required to improve the air circulation effect.
However, the extrusion molding method can only be used to fabricate continuous structures having a uniform cross-sectional area. If the extruded direction of the extrusion molding is defined as a longitudinal direction, through-holes penetrating the extrudate in a direction perpendicular to the longitudinal direction cannot be formed by extrusion molding. If it is intended to form air vents by punching processing, the punching tool is unable to punch holes on the substrate 2 due to the fins 3 protruding from the heat dissipating structure 1. A drill bit can be used to drill holes on the substrate 2, but only one air vent can be done in each process. When the heat dissipating structure 1 must be studded with air vents, the use of a drill bit for drilling holes may require a lot of processing time, and thus fails to meet the demand on yield. Therefore, an enclosed casing fabricated by an extruded heat dissipating structure can only introduce cooling air flows in and exhaust hot air out through the air vents opened on the front and rear panels thereof, so that it is difficult to promote the circulation of the cooling air flows to enhance the air-cooling effect.